1. Field of the Invention
This invention relates to novel 1-phenylcyclohexylperoxy neoalkanoates as a peroxyester and a use thereof as a polymerization initiator for vinyl monomers, particularly vinyl chloride.
2. Related Art Statement
In general, it is known that the peroxyesters can be used as a polymerization initiator for vinyl monomers, which is disclosed, for example, in Japanese Patent Application Publication No. 51-38752 and the like.
In the polymer industry, however, it is desired to increase the productivity of polymers from a viewpoint of economic reasons. Further, it is strongly demanded to develop a more active polymerization initiator for shortening the reaction time and increasing the production volume. The invention is to satisfy such a demand.
Moreover, a more active radical polymerization initiator is desirable to be used for objects other than the above production improvement. That is, such an object is concerned with the production of polyvinyl chlorides having a high polymerization degree.
In general, polyvinyl chlorides having a polymerization degree of not less than 1500 are called as a high polymerization degree product and are known to be particularly excellent in the properties such as mechanical strength, heat stability, dimensional stability, cold resistance and the like. Furthermore, when flexible polyvinyl chlorides are produced by adding a plasticizer to the polyvinyl chloride, rubbery elasticity can be enhanced as the polymerization degree becomes high.
As shown in the following Table 1, the polymerization degree of the polyvinyl chloride is determined by the polymerization temperature, so that in order to obtain a polyvinyl chloride having a high polymerization degree, vinyl chloride should be polymerized at a relatively low temperature of not higher than 50.degree. C. From this reason, it is desired to develop a polymerization initiator having a sufficient activity even at a low temperature.
TABLE 1 ______________________________________ Polymerization temperature (.degree.C.) Polymerization degree ______________________________________ 62 800 57 1000 52 1300 50 1500 45 1900 40 2400 35 3000 ______________________________________
It has hitherto been known to use diisobutyryl peroxide (hereinafter abbreviated as IBPO, Japanese Patent laid open No. 54-11190), acetylcyclohexylsulfonyl peroxide (hereinafter abbreviated as ACSP, Japanese Patent Application Publication No. 40-16795) or the like as a polymerization initiator having an activity even at the above low temperature when polymerizing vinyl chloride monomer.
And also, there is known a compound wherein .alpha.-carbon of carboxylic acid in peroxyester of cumylhydroperoxide is tertiary, such as cumylperoxy neodecanoate (hereinafter abbreviated as CND, Japanese Patent laid open No. 58-120611) or the like.
However, there are some problems in the polymerization methods using IBPO, ACSP and CND as a polymerization initiator. That is, IBPO is very unstable against water and is decomposed by contacting with water, so that the polymerization activity is not held and hence the yield of the polymer is low. On the other hand, ACSP has a problem in view of the hygiene of decomposition products and is poor in the heat stability because the resulting polymer is colored. Furthermore, CND produces a peculiar odor in the polymer because of the decomposition products based on the cumylperoxy group.
In the field of peroxides, it is well-known that a half-valued period of a peroxide (measure on the activity of the peroxide) is remarkably changed by varying the structure of the peroxide.
That is, in case of peroxy esters, the activity can be changed by the structure variation of carboxylic group and hydroperoxy group.
The peroxy esters obtained by the conventional technique and having an activity at a lowest temperature are compounds in which hydroperoxide is cumyl hydroperoxide.
These compounds are active at a low temperature as compared with peroxy esters derived from the other t-alkyl hydroperoxides such as t-butyl hydroperoxide, t-amyl hydroperoxide, t-octyl hydroperoxide or the like when the carboxyalkyl group is same.
That is, a temperature requiring that a half-valued period of 0.1 mol/l of t-butylperoxy neodecanoate (hereinafter abbreviated as BND), t-amylperoxy neodecanoate or t-octylperoxy neodecanoate (hereinafter abbreviated as OND) in benzene is 10 hours (hereinafter referred to as 10 hour halflife temperature) is 41.degree.-47.degree. C., while the 10 hour halflife temperature of CND is as low as 37.degree. C. As previously mentioned, however, there are problems in the polymerization method using CND, so that it is further demanded to develop a polymerization initiator having an activity at a lower temperature in order to conduct low temperature polymerization for the shortening of polymerization time and the increase of production volume.